1. Field of the Invention
The present invention relates to a liquid crystal display device and, more particularly, to a transreflective liquid crystal display device which achieves both transmitting display and reflecting display.
2. Description of the Related Art
As a liquid crystal display device which improves outdoor visibility, a transreflective liquid crystal display device capable of displaying images in both a transmitting mode and reflecting mode is known. In this transreflective liquid crystal display device, a reflecting region and transmitting region are formed by patterning a reflecting metal film formed inside a liquid crystal cell, thereby dividing one display pixel into the reflecting region and transmitting region. Then, the optical characteristic is optimized by changing the ratio of the reflecting region and transmitting region. In addition, a transparent step film or the like is formed in the reflecting region, and the optical characteristic is optimized by changing the cell gap between the reflecting region and transmitting region (by using a multi-gap) (see, e.g., “Jpn. Pat. Appln. KOKAI Publication No. 2003-262852” and “Jpn. Pat. Appln. KOKAI Publication No. 2003-270627”).
In this liquid crystal display device having the multi-gap as described above, a step is formed between the reflecting region and transmitting region, so an alignment defect occurs in the boundary of this step and causes a leak of light. This poses the problem that the contrast decreases. If this step portion is shielded in order to prevent the decrease in contrast, the effective aperture decreases.
Also, since the transparent step film must be formed in the reflecting region in order to change the cell gap, the number of manufacturing steps increases compared to a transmitting liquid crystal display device or the like. Furthermore, reflecting regions are collectively arranged in one portion when forming transparent step films in these reflecting regions, i.e., the arrangement of the reflecting regions is restricted. This influence is particularly large in a high-resolution panel exceeding 300 ppi (pixels per inch). This makes it very difficult to manufacture a transreflective, high-resolution panel.
In addition, a display operation which evenly moves all liquid crystal molecules in the thickness direction of a liquid crystal layer by applying a voltage in the thickness direction is generally disadvantageous in increasing the response speed.